Apparatus and method for the continuous or semi-continuous casting of aluminium

Abstract

Apparatus for the continuous or semi-continuous casting of molten aluminium to form an ingot in the mould ( 8 ) of a casting machine, including a launder ( 4 ), a casting mould and feed means ( 2 ) which is coupled to the launder and extends into the casting mould. The feed means is connected to the underside of a tundish ( 3 ), and the tundish is provided with an inlet member ( 10 ) for admitting molten aluminium from the launder ( 4 ) into the tundish. The tundish is also provided with pressure-reducing means ( 5 ) for lowering the absolute gas pressure in the part of the tundish which is above the molten aluminium admitted into the tundish.

1. Apparatus for the semi-continuous casting of molten aluminium to form an ingot in the mould of a casting machine, the apparatus comprising:
 a launder,  
 a casting mould and  
 feed means coupled to the launder and extends into the casting mould, wherein the feed means are connected to the underside of a tundish,  
 the tundish is provided with an inlet member for admitting molten aluminium from the launder into the tundish, wherein a part of the tundish is located above the molten aluminium admitted into the tundish, and the tundish is provided with pressure-reducing means for lowering the absolute gas pressure in that part of the tundish located above the molten aluminium admitted into the tundish, and  
 wherein the pressure-reducing means, during use, is able to produce an absolute gas pressure in a range from 0.50 to 0.97 bar in the part of the tundish located above the molten aluminium admitted into the tundish, and the casting mould has dimensions for casting an ingot with a thickness of 450 mm or more.  
 
   
   
     2. Apparatus according to  claim 1 , wherein the pressure-reducing means, during use, is able to produce an absolute gas pressure in a range from 0.75 to 0.95 bar in the part of the tundish located above the molten aluminium admitted into the tundish. 
   
   
     3. Apparatus according to  claim 1 , wherein the feed means comprises a casting nozzle formed in such a way that the fluid flow pattern of the molten aluminium into the casting mould is substantially stable and symmetrical. 
   
   
     4. Apparatus according to  claim 3 , wherein the total outlet area of the casting nozzle divided by the horizontal cross sectional area of the casting mould lies in a range from 0.0001 to 0.1. 
   
   
     5. Apparatus according to  claim 1 , for casting an ingot having a length, a width and a thickness, and wherein the casting mould has dimensions for casting an ingot with a width of 2000 mm or more. 
   
   
     6. Apparatus according to  claim 3 , wherein the total outlet area of the casting nozzle divided by the horizontal cross sectional area of casting the mould lies in a range from 0.001 to 0.1. 
   
   
     7. Apparatus according to  claim 1 , wherein the casting nozzle has a dimensionless loss-coefficient in a range of less than 1.6×10 6 . 
   
   
     8. Apparatus according to  claim 1 , wherein the casting nozzle has a dimensionless loss-coefficient in a range of less than 10. 
   
   
     9. Apparatus according to  claim 1 , wherein the casting mould has dimensions for casting an ingot with a thickness of 500 mm or more. 
   
   
     10. Apparatus according to  claim 1 , wherein the casting mould has dimensions for casting an ingot with a width of 2300 mm or more. 
   
   
     11. Apparatus according to  claim 1 , wherein the casting mould has dimensions for casting an ingot with a width of 2500 mm or more. 
   
   
     12. Apparatus according to  claim 5 , wherein the casting mould has dimensions for casting an ingot with a thickness of 500 mm or more. 
   
   
     13. Apparatus according to  claim 1 , wherein the feed means comprises two or more casting nozzles formed in such a way that the fluid flow pattern of the molten aluminium into the casting mould is substantially stable and symmetrical. 
   
   
     14. Method for the semi-continuous casting of molten aluminium to form an ingot in the mould of a casting machine, comprising the steps of:
 casting molten aluminium via a launder and by using feed means which is coupled to the launder and extends into a casting mould,  
 admitting the molten aluminium to a tundish from the launder and passing the molten aluminium from the tundish through the feed means into the casting mold,  
 lowering the absolute gas pressure by pressure-reducing means, above the molten aluminium admitted into the tundish,  
 coupling an underside of the tundish to the feed means and the tundish with an inlet member for admitting the molten aluminium from the launder into the tundish,  
 wherein a part of the tundish lies above the molten aluminium admitted into the tundish and in use, an absolute gas pressure in a range from 0.50 to 0.97 bar is applied in the part of the tundish which lies above the molten aluminium admitted into the tundish, and the aluminium, is cast into a substantially rectangular ingot having a thickness and a width, the thickness being 450 mm or more.  
 
   
   
     15. Method according to  claim 14 , wherein an absolute gas pressure in a range from 0.75 to 0.95 bar is applied in the part of the tundish which lies above the molten aluminium admitted into the tundish. 
   
   
     16. Method according to  claim 14 , wherein the aluminum is cast into a substantially rectangular ingot having a thickness and a width, the width being 2300 nm or more. 
   
   
     17. Method according to  claim 14 , wherein the aluminium, is cast into a substantially rectangular ingot having a thickness and a width, the thickness being 500 mm or more. 
   
   
     18. Method according to  claim 14 , wherein the aluminium is cast into a substantially rectangular ingot having a thickness and a width, the width being 2500 mm or more. 
   
   
     19. Method according to  claim 14 , wherein the outlet opening of the feed means is arranged to lie in between 20 mm and 150 mm below the meniscus of the molten aluminium in the casting mould. 
   
   
     20. Method according to  claim 14 , wherein the outlet opening of the feed means is arranged to lie in a range of 40 to 70 mm below the meniscus of the molten aluminium in the casting mould. 
   
   
     21. Method according to  claim 14 , wherein the inlet of molten aluminium from the launder to the tundish is regulated using a stopper rod, said stopper rod being arranged out of alignment with the feed means. 
   
   
     22. Method according to  claim 14 , wherein the aluminium alloy cast is selected from the group consisting of AA2xxx, AA5xxx and AA7xxx-series aluminium alloys. 
   
   
     23. Method according to  claim 14 , for casting an ingot having a length, a width and a thickness, and wherein the casting mould has dimensions for casting an ingot with a width of 2000 mm or more. 
   
   
     24. Method according to  claim 14 , wherein the casting mould has dimensions for casting an ingot with a width of 2300 mm or more. 
   
   
     25. Method according to  claim 24 , wherein the casting mould has dimensions for casting an ingot with a thickness of 500 mm or more.